The invention relates to a cutterhead or router bit, having profiled insert blades or knives, each having a cutting edge for use in cutting a broad range of nonferrous materials. More specifically, the invention relates to a cutterhead or router bit having profiled insert blades or knives that can be sharpened by re-profiling the cutting edge without changing the original profile, the original cutting diameter of the tool in the radial direction, or the original location of the cutting edge (height or thickness) relative to the axis. The present invention relates to a method and apparatus for sharpening inserts through re-profiling to allow reuse of the insert blade while maintaining the original cutting profile and dimensions.
Generally, cutterheads and router bits are rotating cutting tools designed to perform precision cutting on planar or curved surfaces of a workpiece. Insert cutting tools, comprising one design family of cutting tools, utilize removable cutting blades referred to as knives or inserts. Inserts are commonly, but not exclusively, made from relatively small blanks of various grades of carbide, tantung, or high speed steel ceramic and the like. Some inserts have an insert body with an attached, generally brazed, cutting tip material applied, such as mono or poly-crystalline diamond, other types of manufactured diamond and the like, the cutting materials described above, or other similar materials. Typically, any combination of insert designs may be used on the same cutting tool body.
Cut angles used in metal working are generally different from woods, plastics and other nonferrous materials. Wood varies dramatically in density and grain structure within small areas of a board. Wood knots and wood grain variations provide small visible differences in the wood surface, which may have dramatic effects on blade angles and cutting speeds. Additionally, these wood grain differences vary widely between species of wood. The hook, shear, and back clearance angles are chosen according to the hardness, density and grain variation of the material to be cut. Typically, cutters for metals use negative hook angles. Hard woods, such as hard maple, may also use negative hook angles. Generally, woods, plastics and nonferrous metals have a broader range of possible hook angles, of which the angles for metal working is a small subset.
Industries using wood and related materials, such as MDF, plastics and similar non-ferrous materials, almost universally employ insert-type tools for precision cutting of a profile or a design. Typically, within the family of removable insert cutting tools, the cutting edge extends beyond the cutting tool body peripheral surface as the tool with the inserts rotates on a shank or machine shaft. As the cutting edges contact the workpiece, a chip or shaving is removed from the workpiece. When each blade contacts the workpiece, the blade removes a shaving. The thickness of each shaving depends upon the advance rate of the workpiece and the rotational speed of the cutting tool. The surface of the wood or plastic (workpiece) that is being cut is fed against or in the same direction (commonly referred to as xe2x80x9cclimbxe2x80x9d or xe2x80x9cconventionxe2x80x9d cutting) the cutting tool while the tool rotates.
During use, the inserts may wear down or become damaged. Dull and damaged inserts may damage the workpiece. Thus, cutting inserts require frequent inspection, adjustment, and replacement.
Operating costs depend in large part on how long the insert remains sharp and free of damage before it must be replaced. The operating costs of machines which utilize the thin blades are effected by the cost of the blades, the length of downtime intervals which are required to replace a used blade with a fresh blade, the length of downtime interval required to change the orientation of a blade having several cutting edges, the shape and complexity of the cutting surface, the type of material to be cut, and so on. The length of downtime interval required for exchange or reorientation of blades can be reduced by using holders which can be rapidly inserted into or removed from the body portion of the tool. However, such holders typically assume a singular position for the blade relative to the holder, such that a re-sharpened blade would require adjustment of the entire cutterhead.
The cost of inserts can be kept low by using polygonal pieces of cutting material having one or more cutting edges. However, profile cutting blades typically have a single cutting surface with a unique shape, such that the cost of the blades is significantly higher than the stock blades. While multi-edge indexable inserts can be rotated so that when one cutting edge becomes dull an unused cutting edge can be rotated into position, the profiled inserts typically have a single cutting edge (in some cases two opposing cutting edges) with a unique profile shape. The cost of the profiled inserts is significantly higher than ordinary indexable inserts.
Typically, profiled inserts assume a singular position for the insert relative to the tool body such that the re-profiled or re-faced inserts are changed in one or more dimensions relative to the original insert cutting edge. It is presently possible to re-profile open profiles on inserts without changing the profile; however, the cutting diameter and axial position of the profile cutting edge will change relative to the original cutting edge. It is also possible to sharpen an insert cutting edge by face grinding the insert; however, the profile shape, the radial diameter and the axial position of the cutting edge will change. Thus, the profile inserts are typically designed to be disposable, single-use items.
The present invention includes a rotating cutting tool body (cutterhead or router bit) having one or more precision machined pockets or insert slots for receiving a profiled insert or blade. The profiled insert has a top edge, a cutting profile, a reference edge, and a ramp edge, (not always distinct from one another) and is held in place by a wedge and attachment means. The ramp edge of the profiled insert is aligned against a ramp wall of a pocket in the cutting tool body, and the reference edge is aligned with a reference face of the cutting tool body. As the profiled insert becomes dull, the insert is removed and re-profiled, including the removal of blade material along the cutting profile and along the reference edge to establish a new cutting profile and a new reference edge. The re-profiled insert may then be placed into the pocket in the cutting tool body and advanced along the ramp wall of the cutting tool pocket until the new reference edge of the insert is aligned with the reference face of the cutting tool body. Thus located, the cutting tool with re-profiled inserts maintains a constant diameter, constant profile cutting edge, and a constant axial position.